This invention relates to a method of etching a transparent solid material with a laser beam.
It is generally known to be difficult to etch a surface of a transparent material such as fused silica by conventional laser ablation in which the surface is simply irradiated with a laser beam. One known method to microfabricate fused silica is optical and electron beam lithography, which is a complicated process including patterning a multilayer mask and transferring the pattern to a silica surface by reactive ion etching. In order to develop simpler processes of fabricating fused silica, vacuum ultraviolet laser processing and ultra-short-pulse laser micromatching have been proposed. Also proposed is a laser-induced plasma method in which a metal substrate and a glass are placed in a vacuum chamber and in which the metal is irradiated with a laser beam to generate a plasma for processing the glass. These methods require complicated apparatuses and need high vacuum conditions.
A thermal drilling method is known in which a NiSO4 solution heated with a long pulse laser beam is used to drill fused silica (Ikeno, J. of Seimitsu Kougaku, vol. 55, p.335 (1989)). In order to thermally drill fused silica, it is necessary to use an infrared laser beam having a pulse width of 1 ms and a fluence of 10,000 J/cm2/pulse.
It is, therefore, an object of the present invention to provide a method capable of efficiently etching a transparent material with a relatively low energy laser beam.
Another object of the present invention is to provide a simple method of fine processing a transparent material, which does not require vacuum conditions, which is a one-step process and which is suited for mass production.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a method of etching a transparent solid material having opposing first and second surfaces, comprising irradiating said second surface with a pulsed laser beam having a fluence of 0.01-100 J/cm2/pulse while maintaining said first surface in contact with a fluid capable of absorbing the laser beam so that said first surface is etched with the laser beam incident upon said second surface.